1. Field of the Invention
The present invention relates to a thermal processing apparatus and a method of controlling the same.
2. Description of Related Art
In the manufacture of semiconductor devices, various thermal processing apparatuses are used for subjecting objects to be processed, such as semiconductor wafers, to thermal processes such as an oxidation process, a diffusion process, a CVD process and an annealing process. As one of such processing apparatuses, there is known a vertical-type thermal processing apparatus capable of thermally processing a number of objects to be processed at once. The vertical-type thermal processing apparatus includes: a quartz processing vessel having a lower opening; a lid member configured to open and close the opening of the processing vessel; a holder disposed on the lid member, the holder being configured to hold a plurality of objects to be processed with equal intervals therebetween in an up and down direction; and a furnace body disposed around the processing vessel, and provided with a heater for heating the objects to be processed loaded into the processing vessel.
In order to precisely control a temperature in the furnace body, the following conventional technique has been developed. Namely, a space in the furnace body is divided into a plurality of control zones, and in-furnace temperature sensors are placed in the respective control zones. In addition, a heater is divided for the respective control zones, whereby temperatures of the respective control zones are finely controlled.
However, when the inside space of the furnace body is divided into the plurality of control zones, and the respective control zones are finely controlled, a problem occurs in that it is difficult to control a temperature when it is increased or decreased so that it takes a lot of time to tune control parameters, although a temperature uniformity can be improved when the temperature is stabilized.    Patent Document 1: JP2002-305189A    Patent Document 2: JP2005-188869A
The present invention has been made in view of the above circumstances. The object of the present invention is to provide a thermal processing apparatus and a method of controlling the same, which are capable of improving a temperature uniformity in a furnace body when a temperature is stabilized, and of easily controlling the temperature in the furnace body when a temperature is increased or decreased.